This invention relates to an arrangement for fastening a turbulence vane to a headbox, in which headbox there are openings for the stock flow formed in the plate delimiting the slice chamber, as well as at least one continuous groove running parallel to the width of the headbox and located in the area between the openings in order to fasten a turbulence vane to the said plate on the slice chamber side, while a fastener which is arranged to be placed in the said groove is fitted to the rear edge of the turbulence vane.
Nowadays, special turbulence vanes are used in the slice chamber after the turbulence generator in the headbox of a paper machine. The turbulence vanes are also termed strips or lamellae, a single slice chamber generally containing a total of one to six of them. With the aid of the wall friction of the turbulence vanes, the desired level of turbulence is intended to be maintained to the slice opening and as far as the wire section, so that the fibers in the stock flow will be as randomly oriented as possible when they are discharged from the headbox. This is used to affect the tensile strength of the material being manufactured and the orientation of the tensile strength in different directions in the material. Particularly in the multilayer headboxes used in soft tissue machines, turbulence vanes are also used to separate the different stock layers from each other, which improves the layer purity of the fibers, as well as their orientation.
In the state of the art, a fastener, which is welded or glued to a usually plastic turbulence vane, is used to attach the turbulence vane to the plate delimiting the slice chamber. The turbulence vane is secured, with the aid of a fastener, to a groove machined in the plate. In order to improve the durability of the turbulence vanes and to increase their operating life, attempts are being made, however, to use new kinds of materials, which will resist high temperatures and chemicals. It is impossible, or at least extremely difficult, to glue or weld materials of this kind, such as the so-called fluoroplastics. In addition, welding often causes distortions or strain in the material, which can lead to unpredictable breakages during operation.
FI publication print number 55372 also discloses a fastener, which is glued onto the turbulence vane. The fastening in question is, however, unreliable and it requires a specific kind of groove in the plate. The same publication also discloses another fastener, which is not actually attached to the turbulence vane. The fastening is based on the friction that is created between the turbulence vane and protrusions on the fastener. This fastening is particularly unreliable and its manufacture and installation is difficult. The rotation of the turbulence vane permitted by the fastener is, in addition, extremely limited.
The present invention provides a new type of arrangement for fastening a turbulence vane to a headbox, wherein a turbulence vane can be fastened to a headbox more easily and also more securely than previously.
An arrangement for fastening a turbulence vane to headbox, in which headbox there are openings for the stock flow formed in the plate delimiting the slice chamber, as well as at least one continuous groove running parallel to the width of the headbox and located in the area between the openings in order to fasten a turbulence vane to the plate on the slice chamber side, while a fastener, which is arranged to be placed in the groove, is fitted to the rear edge of the turbulence vane, is characterized in that in the base material of the turbulence vane a fastening retainer is formed, to which the fastener, with a construction arranged to lock onto the fastening retainer, is fitted, and which forms a hinge member permitting the turbulence vane to turn.
In the arrangement there are at least two fasteners and they are arranged to fit entirely into the groove, which is preferably a dovetail groove. The fastening retainer is formed of drill holes, which are arranged in a row running in the direction of the width of the headbox. The drill holes, the diameter of which is 2-6 mm, are machined at a distance of 3-25 mm, from the rear edge of the turbulence vane, and at 5-30 mm, intervals in the direction of the width of the headbox.
In the arrangement the fastener is a coil spring, which is fitted in to the drill holes forming the fastening retainer, the coils of the coil spring forming the construction. The pitch of the coil spring, which comprises acid-resistant steel, is the distance between the drill holes, or a multiple of the distance.
The fastening retainer is formed by at least one groove running parallel to the width of the headbox and machined in the upper and/or lower surface of the turbulence vane. The groove is machined at a distance of 5-25 mm, from the rear edge of the turbulence vane.
The fastener which has an essentially circular cross-section is of a plastic material. A construction locking onto the fastening retainer is shaped in a throat formed in it.
The length of the fastener running in the direction of the width of the headbox is 50-350 mm, and that these are arranged in the turbulence vane at intervals of 100-500 mm.
In the arrangement according to the invention, special fasteners are used, by means of which gluing and welding are avoided. Thus, it is possible to use materials resistant to high temperatures and various chemicals, which it would be difficult to glue, weld, or join in other ways. According to the invention, there are constructions corresponding to each other in both the turbulence vane and the plate, which lock into each other. Gluing and welding are then unnecessary. In addition, the fastener can be manufactured from a different material than the turbulence vane. The fasteners can also be manufactured in several different ways and they permit thermal expansion in adjacent structures. In addition to attachment, the fastener also forms a hinge member, which permits the turbulence vane to turn freely. Further, the fastener according to the invention is suitable for use directly in the existing conventional grooves in a headbox.
These and other features and advantages of the invention will be more fully understood from the following detailed description of the invention taken together with the accompanying drawings.